Tristan Walker, Foursquare’s 25-year-old head of business development, graduated from Stanford Business School over the weekend. If you’re among the many companies waiting for a call back from the geo-social start-up, Walker’s commencement is partly to blame. Or so founder Dennis Crowley told the crowd at CM Summit during Internet Week in New York.

“For everyone that’s tried to get in touch with Tristan, you know what a bottle neck it is,” Crowley said. He added, “It’s not that we don’t think your ideas are good, it’s just that we don’t have time to answer all of them.”

To be fair, Walker would have a hard time responding to all marketer requests even if he wasn’t balancing his job with school commitments. A spokesperson for New York City-based Foursquare said inbound requests from businesses are coming in at the rate of hundreds a day. For a company with fewer than 30 employees, that’s tough to handle. (See today’s accompanying story: “Foursquare Checks In With Marketers“)

Late last week, between having his gown fitted and adjusting his tassle, Walker paused to answer a few questions for ClickZ readers.

ClickZ: When it comes to creating partnerships with large brands, how do you decide who to work with?

Tristan Walker: When we started, we wanted to work with charter brand advertisers in various verticals (e.g. CPG, entertainment, publishing) that really understand how to do social – Starbucks for retail, Bravo for entertainment, Pepsi for CPG, New York Times for publishing, etc. By working closely with a set of unique brands within these verticals, we’ve been able to develop a great product. We have a lot of work to do, with brands across various other verticals, for example, but we’re getting there!

CZ: That certainly has the ring of a scalable ad model.

TW: We are working with our brand partners to develop ideas for a product that can scale, but we’re not actually in the process of developing any self-service platforms for brands right now. Our focus is on continuing to support the partners we currently have, and looking at how it might make sense for us to scale brand integrations in the future.

CZ: How many large relationships of the Starbucks variety do you have in development now? How often can we expect to see them roll out going forward?

TW: We have a good number of brands in the pipeline, particularly in retail. We’re working with brands/retailers to think about how we can help engender loyalty. We’re hoping to really innovate in this space in the next few months. We’ll continue rolling out brand integrations in a variety of ways, working closely with brands to ensure that both we and they feel comfortable with the campaigns.

CZ. I know you’re moving away from creating branded badges. Do you expect to do any going forward? Could that possibly be a super-premium sponsorship option for you?

TW: We absolutely plan on continuing with branded badges, but we are taking our time to determine what the platform for badges should look like in the future (super premium or not). We’re continuing to discuss the best way to handle branded badges with the fantastic advertisers we’ve been working with thus far.

CZ: Are these all paid deals?

TW: Not all. We do charge for sponsored badge integrations.

CZ: When do you move to New York?

A. I’ll be moving to New York next week for the summer, but after August I’ll be based in the Bay Area in sunny Palo Alto!